Cell‐bound exopolysaccharides of Lactobacillus brevis KB290 enhance cytotoxic activity of mouse splenocytes

AIMS: This study aimed to identify the main active component of Lactobacillus brevis KB290 (KB290) that is responsible for enhanced cell‐mediated cytotoxic activity of mouse splenocytes Live KB290, a probiotic strain derived from a Japanese traditional pickle, was previously reported to modulate innate immune responses as affecting on cell‐mediated cytotoxic activity of mouse splenocytes. METHODS AND RESULTS: We used live KB290, heat‐killed KB290, a derivative strain (Lact. brevis KB392) with different amounts of cell‐bound exopolysaccharide (EPS‐b), and a crude extract of EPS‐b from KB290 cell surface. Female BALB/c mice were fed a diet containing 10¹⁰ CFU live KB290, 10¹⁰ CFU live KB392, 15 mg heat‐killed KB290 or 600 μg crude extract of EPS‐b for 1 day. Live KB290 (P